Hazrat Moulana Ashraf Ali Thanwi (rahmatullahi ‘alaih) once mentioned:
Allah Ta‘ala says in the Qur’aan Majeed:
وَ اعۡتَصِمُوۡا بِحَبۡلِ اللّٰهِ جَمِیۡعًا وَّلاَ تَفَرَّقُوۡا
Hold firmly to the rope of Allah all together and do not be divided. (Surah Aal-e-Imraan v. 103)
The benefit of unity mentioned in this verse will not be acquired by merely bringing people together. Rather, the benefit of unity will be acquired through bringing people together and uniting them upon the rope of Allah (i.e. uniting them upon practising true deen).
Hence, it is a futile exercise to try and bring people together merely for the sake of unity (when their deeni views and objectives are poles apart). Instead, the purpose of unity is to unite people upon the truth, and this is what is being referred to by “Hold firmly to the rope of Allah all together and do not be divided” mentioned in this verse of the Qur’aan Majeed.
In other words, the first step towards achieving unity is to determine which group is upon haq (the truth) and which group is upon baatil (falsehood). (Thereafter, both groups should be dealt with correctly.) The group that is upon baatil should be invited towards the haq, and the group that is upon haq should not be criticized or condemned in any way. (When this is the approach adopted, then unity will be achieved.) Hence, we understand that this verse refers to a specific type of unity and not general unity by merely bringing people together without the correct deeni objective being achieved, merely for the sake of unity.
(Malfoozaat Hakeemul Ummat 14/56)